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Daveinet 07-26-2010 12:17 PM

Lightning Strike??
What does everyone do about the potential for lightning strikes? I read about sailing in storms, sailing around the world. But I was always told if there is a chance of lightning, you don't want to be near the water, especially with a mast sticking up saying Hey, strike here! I've been struck by lightning once in life, and really don't want that to happen again, so my question is, Is the potential for lightning strike as bad as I perceive that it is, or does everyone just ignore the possibility? What does everyone do?

trailblazer1229 07-26-2010 12:35 PM

I asked my instructor this question. He said that the mast on our particular boat was grounded to the keel and the keel should dissapate the strike thorugh the water. Knowing a bit about how electricity works, I did not see a grounding wire and didn't know what he was talking about. I have seen a bit on this board, and you will get some interesting answers, the one I keep refering to and laughing at is keep sailing and "hope for the best." Seeing as how you have been struck once already and prone to strkies in the future, I think you are right when you want to find the best possible answer. If you do a search, you will find a lot of info.

Jeff_H 07-26-2010 01:20 PM

Boats get struck by lightning all the time. The amount of damage depends on a variety of factors, and there are no guarantees.

As a general rule of thumb, the best advice is to seek shelter off the boat, but of course that is not always practical. Failing that the general advice is to stay away from metal objects. That only goes so far.

There are all kinds of gimmicks out there such as these little brush things for the mast head, but the current thinking is that none of this stuff does much good.

The way the boat is built can help some. If there is a direct path for the lightning to pass through the boat to the water, the damage is less likely to be structural than if there is not and the path of the lightning passes through the fiberglass or a bonding system.

So for example my boat was hit while out of the water. Our best guess is that the lightning hit the masthead, came down the mast itself, through the aluminum mast step, through the stainless steel beam that the mast step is bolted to below the cabin sole, through the stainless steel keel bolts that pass through the stainless steel beam and out through the lead keel. While the electronics were fried, there was no other damage.

By the same token, when I worked in boat yards in Florida, the yard did an emergency haul-out of a boat that had been hit by lightning. The lightning had apparently passed through the shrouds and chainplates, into the bonding system and in part passed through the thru-hulls and in part passed through the hull. The copper bonding straps were melted and had gotten hot enough to set the bulkhead and fiberglass on fire. The thru-hull had 'de-zinced' and could be crumpled in your hands (it held until the boat was hauled and was discovered during the survey. A portion of hull was riddled with small almost microscopic pin holes where the electricity passed through. Since then I have heard of other cases of 'worm holes' in glass boats struck by lightning.

Recently an article in Sail Magazine discussing lightning and while a little superficial, it did provide a good general description.


lydanynom 07-27-2010 09:17 AM


Originally Posted by Jeff_H (Post 625869)
the current thinking is that none of this stuff does much good.

Here in the midwest we get scattered thunderstorms virtually every afternoon during parts of the summer, so I have done a ton of reading on this topic while trying to find a way to stay out on the lake while they blew through.

The short answer is as Jeff said above, nothing you can add on really makes a difference. Get off the water if you can, cringe and hope for the best if you can't. The good news is that serious injury or death is surprisingly uncommon, considering how relatively often sailboats do get hit. The bad news is that serious structural damage is extremely likely.

jimmalkin 07-29-2010 12:31 PM

I don't think "hope for the best" is really a laugh producer. As Jeff and Lydanynom said above, there really isn't much you can add on to the boat that is sure to help. Lots of articles, lots of chat but every discussion I've had with boat yards ends with "keep from touching anything metal during the strikes."

I've had the nervousing experience of sailing through too many thunder/lightening storms with no port in reach and no way of getting out of the storm path (which is always a matter of guess work anyway.) There's little time to unplug all the electronics and put them in an oven to shield them from the power shock of a direct hit, there's little time to do much except hope for the best, don't touch metal and make sure all your gear is tied down and shipshape. And despite the nervousness, power of the spectacle at sea is incredible.

Best of luck - which may be the best there is to offer!

paulk 07-29-2010 03:50 PM

We had friends whose boat - a Bristol 35.5 -(with them on it) was hit by lightning last Sunday, July 25, at Duck Island Roads, an anchorage off Westbrook CT, about 01:00AM. A witness who went out to to speak with them later that morning said he saw the bolt hit and that the boat glowed. He called 911, thinking that the boat's propane tank had exploded. (It had not.) Our friends, on board and awake (who could sleep with all those bright lights and thunder) thought the bolt hit nearby, then heard all their electronics popping and frying. The masthead VHF antenna twisted into a corkscrew, with the insides of the ceramic housing totally vaporized. The police showed up to check on them that night and again the next morning, but the boat appeared to be OK except for the overcooked electronics. Don't know if they had engine problems or not. They hauled to check for dezincing, (mentioned above) and continued on their cruise later on Monday. Craig Smith, knowledegable about extreme waves and lightning, seems to think that the backstay of the Bristol 35.5, running down to a big external chainplate at the transom near the swim ladder (which may have been down, too ) provides a nice path for a hefty electric current to take when the need arises. A cushion left near the backstay was singed. Our friends are happy to still be sailing, though it's going to take almost three dozen boat unit$ to fix their electrical system and replace the components.

TQA 07-29-2010 04:07 PM

If it is something that really REALLY worries you buy a steel boat.

The path to "earth" is not interrupted by fibreglass so hull damage is most unlikely. If in side when you are hit you are in what is called a Faraday Cage and if you have to be struck then that is a good place to be. [ You might be deaf for a day or two - ask me how I know this.]

But there is problem that only steel boat boats may suffer from subsequent to a strike, the hull can become a strong magnet and your compasses are useless. Mine pointed to 137 degrees regardless of my actual heading.

Jeff_H 07-29-2010 05:23 PM

Actually, almost nothing is more scary to me than to be on a steel boat in a lightning storm. A lightning strike on a steel boat is especially dangerous. The large voltage through the steel can literally electric arc cut the plating and can instanteously eletrolysize away sections of the hull. I looked a steel boat that had was being salvaged in South Florida years ago and a large chunk of the bottom plating looked like swiss cheese. The owner was badly burned and one of the crew was left in critical condition after receiving a major shock thought to be from induced current through a portion of the hull.


chris31519 08-01-2010 01:13 PM

Don't forget that water - especially fresh water - is not a good conductor. When you earth the mast you have to consider what it's earthed to, it needs to be able to dissipate the current. I sail often in a large shallow lake and drag a chain to the lake bed when a storm comes, (as well as earthing the mast to the iron keel that has a large surface area). There's lots of good info on the Internet.
e.g Lightning Protection on Sailboats

killarney_sailor 08-01-2010 01:54 PM

We were hit by lightning on the way to Bermuda many years ago. If it makes people better (and perhaps it should) the remarkable thing was not that we were hit but that it took so long to be hit. Bolts were hitting the water around us constantly for 20 minutes or so before we were hit. Damage was not too bad, nav lights blown out, vhf not working, voltage regulator cooked. I saw it hit the windex which blew off. one of the crew was holding the wheel with considerable rainfall in the cockpit and bare feet and felt nothing.

There just seem so many random factors associated with lightning that it is virtually impossible to draw any firm principles for dealing with the subject.

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